Conventionally, the seat sliding device used in a rear seat of a vehicle having three-row seats has lower rails that are inclined such that the front side is lower than the rear side. In contrast, the seat sliding device used in a front seat such as a driver's seat has lower rails that are inclined such that the rear side is lower than the front side. In a seat sliding device with inclined lower rails as mentioned above, the force (load) required to slide the seat forward when adjusting the seat position forward is different from the force (load) required to slide the seat rearward when adjusting the seat position rearward.
The vehicle seat sliding device of Patent Document 1 has lower rails inclined such that the rear side is lower than the front side and also has a slide resistance adjusting mechanism. The slide resistance adjusting mechanism has multiple protrusions, which are provided on the lower rails, and balls, which are arranged on the upper rails and pressed against the protrusions by compression springs. Each protrusion has an inclined surface, against which the ball abuts when the upper rail is slid forward (upward), and a resistance surface, against which the ball abuts when the upper rail is slid rearward (downward). The inclination angle of the resistance surface with respect to the sliding direction of the upper rail is greater than that of the inclined surface. When the upper rail is slid, the ball goes over the protrusion. The resistance applied to the ball by the resistance surface when going over the protrusion due to rearward movement of the upper rail is greater than the resistance applied to the ball by the inclined surface when going over the protrusion due to the forward movement of the upper rail. This equalizes the force (load) required to slide the seat forward and the force (load) required to slide the seat rearward.